A single-track railway is where trains in both directions share the same track. Single track is normally used on lesser-used rail lines, often branch lines, where the traffic density is not high enough to justify the cost of building double track.

Single track is significantly cheaper to build, though it has operational disadvantages. If the single-track section is say 15 minutes long, the line would have capacity for only two trains per hour in each direction. Double track can allow up to 15 trains per hour in each direction if signal boxes are four minutes apart. This hindrance on the capacity of a single track may be partly overcome by making the track one-way on alternate days, if the single track is not used for public transit.

Long freight trains are a problem if there are not enough long passing stretches. Other disadvantages include the spread of delays, since if one train on a single track is delayed, any train waiting for it to pass also will be delayed. Also, single track does not have a "reserve" track that can allow a reduced capacity service to continue if one track is closed.

Single track may refer to: